A laboratory is being developed to allow examination of the single channel properties of a variety of epithelial ion channels by fusing cell membrane fragments to planar bilayer membranes. The amiloride sensitive sodium channel, found in many epithelia, will be characterized first. Measurement of the single channel conductance as a function of membrane voltage, sodium concentration, pH, ionic composition of the bathing media and membrane surface charge will provide information regarding direct control of this important sodium entry mechanism. Secondly, by determining the ion selectivity of the carrier under the conditions listed above and after specific group modification, one can begin to define what elements are essential for providing both the selectivity and conductivity of a channel. A variety of biochemically characterized channels will also be studied to develop basic criteria for specific channel properties.